Question

4.) a) (10 pts) Consider the three constitutional isomers of dioxane (CHO) One of these constitutional isomers (Isomer A) is stable under basic conditions as well as mildly acidic conditions and is commonly used as a solvent. One of these (Isomer B) is only stable under basic conditions but undergoes hydrolysis under mildly acidic conditions. The remaining isomer (Isomer C) is extremely unstable and potentially explosive. Identify each isomer (label each as AB or C) and explain the properties of each compound.

Answer 1

These compounds are called 1,4 dioxane or p-dioxane

                                            1,3 dioxane or m-dioxane

and                                       1,2 dioxane or o-dioxane.

Given that the isomer - C is highly unstable and explosive. We know that the peroxides are explosive and unstable. Here we have the peroxide link in 1,2 dioxane. [ - O - O- ]

Hence the isomer- C is 1,2 dioxane.

Given that the isomer-A is stable at basic conditions as well as mild acidic conditions. We have the 1,4, dioxane which is having two ether linkage -R-O-R and hence it is stable in basic as well as acidic conditions.

Thus the isomer -A is 1,4 dioxane

Given that the isomer -B is stable at basic conditions but hydrolyse in mild acidic conditions. The 1,3 dioxane is having a ketal structure -RO-C-OR- that is single carbon linked to two alkoxy groups. We know that ketals are susceptable to hydrolysis under acidic conditions.

Thus the isomer - B is 1,3 dioxane.

ISOMEALA) 4 diasane 150MER B 13 diename ISOMER-C 1 diename